Method of making an off-wall spacer cage

ABSTRACT

A method of making a spacer cage is disclosed. The method may include providing a tube having an outer diameter, a first second, a second section and a middle section having a first end connected to the first section and a second end connected to the second section, cutting the middle section to form strut elements of the spacer cage and cutting a plurality of longitudinal slits in the first and second sections to allow radial expansion of the first and second sections, expanding the tube using a mandrel, heat setting the tube while on the mandrel, and subsequent the heat setting, removing the first and second sections from the tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S. Provisional application Ser. No. 61/546,404, filed Oct. 12, 2011, the entirety of which is incorporated herein by reference.

FIELD

The present invention relates to methods of manufacture for expandable spacer cages used in medical devices.

BACKGROUND

Many medical devices use an expandable or self-expanding structure that includes struts or the like. For example, certain renal nerve modulation devices use an expanding spacer cage for positioning electrodes within a blood vessel while keeping them spaced from the wall of the vessel.

Simplified and alternative construction techniques for such expanding structures are therefore desirable.

SUMMARY

The disclosure is directed to methods of making and precursors for making expandable and self-expanding structures such as spacer cages for use in medical devices.

Accordingly, one illustrative embodiment is directed to a precursor formed from a cylindrical tube having a first end and a second end and a longitudinal axis extending from the first end to the second end. The precursor includes a primary section which is formed into strut assemblies or the like and generally includes a plurality of slits extending between the two ends of the primary section. The precursor also may include one or two end sections which are configured to allow radial expansion of the precursor when, for example, expanded with a mandrel having a larger outer diameter than the inner diameter of the precursor. The one or two ends sections may be configured for radial expansion by providing a plurality of longitudinal slits that allow for an accordion-like expansion.

Each strut assembly may include a first main strut section, a second main strut section and a pair of spacer strut sections extending between the first main strut section and the second main strut section, and may further include an electrode support strut section extending from the first main strut section between the pair of spacer strut sections.

Each end section may include an even number of elongate elements, each elongate element adjacent to two other elongate elements and having a first end connected to only one of the adjacent elongate elements and a second end connected to only the other of the adjacent elongate elements.

One illustrative embodiment pertains to a method of making a spacer cage, that may include the steps of providing a tube having an outer diameter, a first second, a second section and a middle section having a first end connected to the first section and a second end connected to the second section, cutting the middle section to form strut elements of the spacer cage and cutting a plurality of longitudinal slits in the first and second sections to allow radial expansion of the first and second sections, expanding the tube using a mandrel, heat setting the tube while on the mandrel, and, subsequent the heat setting, removing the first and second sections from the tube.

Further steps in the illustrative method may include the steps of, subsequent to the heat setting and prior to the removing of the first and second sections, removing the mandrel, attaching a first tube segment having an inner diameter to the first end of the middle section, and attaching a second tube segment having an inner diameter to the second end of the middle section. The mandrel may have a first cylindrical section, a second cylindrical section and a middle section having a larger cross-sectional area than either the first or second cylindrical sections, the middle section being disposed between the first and second cylindrical sections and may also include tapered or conical sections between the first cylindrical section and the middle section and between the second cylindrical section and the middle section. The mandrel may include grooves or other depressions in the outer surface of the middle section.

The step of attaching the first tube segment may further include the step of disposing the first tube segment over the middle section and attaching an inner surface of the first tube segment to an outer surface of the middle section, wherein the outer diameter of the tube is equal to the inner diameter of the first tube section or wherein the outer diameter of the tube is greater than the inner diameter of the first tube section or wherein the outer diameter of the tube is less than the inner diameter of the first tube section.

A method may further comprise the steps of, subsequent to the heat setting and prior to the removing of the first and second sections, attaching a third tube segment to the first end of the middle section, and attaching a fourth tube segment to the second end of the middle section. A catheter tube may be attached to the middle section subsequent to the step of removing the first and second sections at either the first end of the middle section, the second end of the middle section, or both ends of the middle section. In some embodiments, the catheter tube or other components may be attached to the middle section through one or both of the third and fourth tube segments.

The above summary of some example embodiments is not intended to describe each disclosed or contemplated embodiment or every implementation of the invention.

BRIEF DESCRIPTION OF DRAWINGS

The invention may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which:

FIG. 1 is a schematic view illustrating an example medical device in situ;

FIG. 2 illustrates a distal end of an example medical device system;

FIG. 3 illustrates the distal end of the example medical device system of FIG. 2 in situ;

FIG. 4 is a side view of a precursor that may be used in the construction of a medical device system;

FIG. 5 is a schematic view illustrating manufacturing steps using the precursor of FIG. 4;

FIG. 6 is a side view illustrating a step in an example manufacturing process;

FIG. 7 is a side view illustrating a step in an example manufacturing process;

FIG. 8 is a side view illustrating a step in an example manufacturing process;

FIG. 9 is a partial view illustrating an example precursor; and

FIG. 10 is a view of an example mandrel that may be used in a manufacturing process according to one embodiment.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in the specification.

All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may be indicative as including numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

Although some suitable dimensions ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless 5 the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary.

Embodiments of the disclosure are directed to a particular component or set of components and methods of manufacture thereof. This component or set of components is however generally a part of a larger device, system, or assembly and an example assembly 10 is illustrated generally in FIG. 1. FIG. 1 is a schematic view illustrating a renal nerve modulation assembly 10 that may include components manufacturing according to embodiments described herein, and includes, as better seen in FIG. 2, a renal ablation system 12. Assembly 10 is an example assembly, and the particular assembly 10 illustrated includes a self-expanding renal ablation system 12 that can expand to an enlarged, operative state when released from constraint such as by withdrawing a sheath. Other example systems (not illustrated) may be actively deployed and include a pull wire or balloon deployment element. Further, as discussed below, the methods and components discussed herein are not limited to renal nerve modulation assemblies/systems.

The renal nerve modulation assembly 10 may also include other components such as a sheath 14 (which may take the form of a guide catheter), a conductive element 16, a control and power element 18, and return electrode patches 20. The components that may be manufactured according to embodiments described herein may be better seen with reference to FIG. 2, which illustrates the distal end of the renal nerve ablation system 12, in which includes one or more strut assemblies 24 attached to a shaft 21. Each strut assembly may include spacer struts 26 and an electrode strut 28. An electrode 30 may be made integral with the electrode strut 28 or may be a separate element attached to the electrode strut 28. Other elements may include an atruamatic distal end 22 and an inner expansion element 32. The distal end of the system 12 is illustrated disposed within a blood vessel 34 in FIG. 3.

Strut assemblies 24 are illustrative of components that may be manufactured using embodiments described herein. Each strut assembly 24 may include two spacer struts 26 and an electrode strut 28 and may include an integral electrode 30. The strut assemblies 24 are generally elongate members that may be cut from the same tube in the relative orientation of the final assembly. However, the strut assemblies 24 are separate components that are subsequently assembled into the system 12. Further, the strut assemblies 24 are shaped in some manner prior to assembly. Any component or set of components that share the characteristics of being able to be cut from a single precursor in the final orientation may advantageously be made according to embodiments described below. It can therefore be seen that the disclosure is not limited to the strut assemblies or system described herein but may be applied to other suitable components. For example, FIG. 9 illustrates a primary section 38 in which the electrodes are not integral with the electrode struts. Instead the electrode struts 54 are cantilevered and allow for the assembly of electrodes to the electrode struts at a later state of manufacturing.

In general, a method of manufacture according to an embodiment of the invention may involve the following steps. A tube or other precursor is cut to form a primary section of the tube into multiple main strut assemblies. The tube may include any suitable material, for example, Nitinol, stainless steel, Ti 6-4, Beta 3 Ti, MP35N, Elgiloy, titanium, gold, or silver. An end of the primary section abuts a first section that is cut or otherwise formed to allow radial expansion and may also abut on the opposite end a second section that is also cut or otherwise formed to allow radial expansion. A shaping mandrel is inserted through the cut tube, which insertion is made possible by the expandable first and/or section sections, and the main strut assemblies are heat set or otherwise formed around the shaping mandrel. The shaping mandrel is removed and the ends of the middle section are fixed in relative position to each by, for example, the fastening of polymeric tubular sections to the first and second ends of the primary section. The first and second sections are removed from the primary section. At this point, the primary strut assemblies are not fixed to each other by any material of the tube precursor but are nevertheless retained in relative position to each other. The main strut assemblies may then be fixed to a catheter tube or otherwise assemblies into an operative system. It can be appreciated that in this method of manufacture, the main strut assemblies are always in the proper relative position to each other and do not need to be individually oriented and joined to the operative system assembly.

A more detailed explanation of a method of manufacturing may be had with reference to various figures, beginning with FIG. 4. FIG. 4 illustrates a tubular precursor 36 which has been cut to form a primary section 38 and two end sections 40 abutting the primary section. The tubular precursor 36 may be made from stainless steel, nitinol, polymer or other desired material. The primary section 38 is so called because it is the section in which strut assemblies 24 are formed which will be assembled into the system assembly. The strut assemblies 24 depicted in FIG. 4 have a different configuration from that of FIG. 2, for example. In the strut assemblies 24 of FIG. 2, the electrodes 30 are not integral with the electrode struts 28 on which they are disposed and all the electrodes 30 are at the same longitudinal position on the system 12. In contrast, the electrodes 30 of FIG. 4 are at different longitudinal locations and are integral with the electrode struts 28. It should be apparent that one can make the main strut assemblies 24 of FIG. 2 or any number of variations by using a similar process but by forming a different pattern in tubular precursor 36. Neither the strut assemblies 24 of FIG. 2 or FIG. 4 have proximally oriented free ends; this geometry helps to avoid catching a free end of a strut assembly 24 on an edge of a retrieval sheath. In other embodiments, the tubular precursor 36 used may have a circular cross-sectional shape, a square cross-sectional shape or other suitable shape.

The primary section generally includes a plurality of slits 68 extending from a first end 64 of the primary section 38 to a second end 66 of the primary section 38. These slits 68 separate each strut assembly 24 from the others. Further slits may be included to define other features such as spacer struts, electrode struts, electrodes and the like as desired. Such slits may be formed by laser cutting or other suitable forming technique.

Tubular precursor 36 is shown as having the primary section 38 between two end sections 40. Each end section 40 is cut to allow for easy radial expansion when expanded by, for example, sliding the tubular precursor 36 over a mandrel (such as that of FIG. 10) that has a larger maximum diameter than the inner diameter of the tubular precursor 36. It can be seen that each end section 40 is composed of generally elongate members 42 that are joined to adjacent elongate members at alternating ends 44 so as to allow an accordion-like expansion of the cut tubular precursor 36. Such a configuration may allow for a purely elastic deformation of the end sections 40 over the contemplate range of diameters. Some plastic deformation may take place as well. Any suitable configuration that allows radial expansion may be used. For example, many of the expandable stent strut configurations may be suitable for use as end sections 40.

Further, in some instances it may be appropriate to form a cut tubular precursor that includes only the primary section 38 and one end section 40 at a first end 64 of the primary section 38. An end of the tubular precursor 36 would in this instance be the second end 66 of the primary section 38. In other instances, a tubular precursor might include a primary section 38 between two end sections 40 as illustrated. However, only one end section 40 need be cut, leaving the other end section 40 an uncut tubular section. Such a configuration may be appropriate in instances where a mandrel can be slid in and out from one end of the tubular precursor 36.

In FIG. 5, the expansion of the tubular precursor 36 is schematically illustrated. Prior to shape setting, the tubular precursor 36 has an outer diameter at A and may be readily expanded to a larger diameter such as that indicated at B by inserting a tapered mandrel to push the strut assemblies apart. A mandrel such as that shown in FIG. 10 may be used to achieve a desired shape. The center portion of the primary section 38 may be pushed out to the diameter indicated at B. The adjoining portions of the primary section 38 may taper along the C line and the outer portions of the tubular precursor 36 may be at the A diameter once the mandrel is centered. Other external clamps or fixtures (not illustrated) may be used to hold the tubular precursor 36 in the desired position as well as the mandrel. Once the desired position is achieved, the tubular precursor 36 may be heat-set, thermoformed or otherwise shape set to achieve the desired configuration. In this example, once the strut assemblies 24 are heat-set, they will be biased to an expanded configuration.

As illustrated in FIG. 6, once the strut assemblies 24 are heat set, they may be fixed relative to each other at one or more locations along the primary section 38. For example, a first tubular section 46 may be fixed to a first end 64 of the primary section 38 and a second tubular section 48 may be fixed to the second end 66 of the primary section 38. In one contemplated alternative (not illustrated) third and fourth tubular sections are fixed inside the first and second tubular sections to sandwich the ends of the strut assemblies such that the first end 64 is sandwiched between and affixed to the first tubular section 46 and a third tubular section (not illustrated) and the second end is sandwiched between and affixed to the second tubular section 48 and a fourth tubular section (not illustrated). The tubular sections 46/48 may be polymeric sections or other suitable material. Suitable materials for the tubular sections include polymers, polyimide, liquid crystal polymer, vectran, ceramic, polysolfone, and PEEK. The tubular sections may be affixed to the strut assemblies using any suitable method and materials, such as gluing or thermal bonding. Suitable bonding agents may include epoxy, cyanoacrylate, hot melt adhesives, polyurethane adhesives, silicone adhesives and thermoplastics. The tubular sections 46/48 may be used in a further manufacturing step to join the strut assemblies to other portions of an operative system and thus form a part of the final assembly. In another contemplated embodiment, the tubular sections 46/48 may be removed once the strut assemblies 24 are fixed to other components of the operative system. In such embodiments, the tubular sections 46/48 may be replaced by any suitable components that can be used to retain the strut assemblies in fixed relative position. There may be, for example, a single tubular section that extends for substantially the whole length of the strut assemblies. Alternatively, the strut assemblies 24 may be substantially encased in wax or like material that can be easily removed when desired.

At this step of fixing the strut assemblies 24 relative to each other, the relative radial positions of the strut assemblies 24 may be adjusted prior to applying tubular sections 46/48 or the like. In one embodiment, the strut assemblies 24 are fixed at the same diameter as the tubular precursor 36. In another embodiment, the strut assemblies 24 may be fixed at a smaller or at a greater diameter as desired. Tooling such as a mandrel or clamps may be used to adjust the diameter of the tubular section to adjust the radial positions of the ends of the strut assemblies while retaining the same relative circumferential positions. In some embodiments, one end can be fixed at one diameter while the other end is fixed at a second different diameter. Once the strut assemblies 24 are in the desired position, tubular sections 46/48 or the like may be applied to fixed the positions of the strut assemblies 24 relative to each other.

After tubular sections 46/48 or the like are applied, the end sections 40 may be cut off as illustrated in FIG. 7. At this point, the strut assemblies 24 are fixed relative to each other but are not attached to each other with any material of the tubular precursor 36. They are joined together and held only by tubular sections 46/48 or the like. The strut assemblies 24 may then be joined to another component such as catheter tube 50, as illustrated in FIG. 8 by for example melt bonding or gluing tubular sections 46/48 to the catheter tube 50. It will be recognized that this Figure is purely illustrative and many variations are possible. For example, each end may be joined to a different component. What is pertinent is that the plurality of strut assemblies are fixed to components of the system without having to align and fix each strut assembly individually.

FIG. 10 illustrates an example mandrel 56 that may be used in a manufacturing process in which a tubular precursor 52 such as that of FIG. 9 may be formed. The mandrel 56 includes cylindrical end sections 58 smoothing joined to a central section 62 by tapering or conical sections 60. Central section 62 includes grooves 65 that may be used to heat set electrode struts 54 at a different radial location than the surrounding struts. The electrode struts 54 may be pressed into grooves 65 by clamps or other tooling (not illustrated). Depending on the final desired shape, mandrels and tooling of different configurations can readily be provided. The mandrel central section 62 has a larger outer diameter than that of the tubular precursor 52. The expandable end sections 40 allow for the insertion of such a mandrel 56 into the tubular precursor 52 to permit the shaping of the strut assemblies as a group.

Those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly departure in form and detail may be made without departing from the scope and spirit of the present invention as described above and in the appended claims. 

What is claimed is:
 1. A method for manufacturing a renal nerve modulation device, the method comprising: providing a tubular member; cutting the tubular member to define a plurality of strut assemblies connected by one or more expandable end sections; wherein each of the strut assemblies include a main strut, a spacer strut, and an electrode strut; attaching at least one tube to the tubular member adjacent to at least one of said expandable end sections; removing one or more of said expandable end sections from the tubular member to define a cage member; and attaching the cage member to a catheter shaft.
 2. The method of claim 1, wherein cutting the tubular member to define one or more strut assemblies includes cutting a plurality of longitudinal slits in the tubular member.
 3. The method of claim 1, further comprising disposing the tubular member on a mandrel and wherein disposing the tubular member on a mandrel includes expanding the tubular member.
 4. The method of claim 3, further comprising heat setting the tubular member.
 5. The method of claim 1, wherein the tubular member includes a main body, a first expandable end section, and a second expandable end section, and further comprising attaching a first tube to the tubular member adjacent to the first expandable end section and attaching a second tube to the tubular member adjacent to the second expandable end section.
 6. The method of claim 5, wherein removing the one or more expandable end sections from the tubular member to define a cage member includes removing the first expandable end section, the second expandable end section, or both from the tubular member.
 7. The method of claim 6, wherein attaching the cage member to a catheter shaft includes disposing the first tube, the second tube, or both adjacent to the catheter shaft. 